Tony's Little Big Green Monster
by Merciful Misaki
Summary: Tony Stark has dragged Bruce Banner into yet another sketchy experiment, but this time Tony doesn't seem so honest. Unwilling to leave Tony's side when called, this big green oaf is about to receive a run for his money and learn the hard way true meaning of the quote "Falling in love and having a relationship are two different things."
1. Chapter 1: The Project

Chapter 1

"Tony, this isn't going to work."

"Calm down, why is it that you only have a pair of balls when you turn into the big guy."

"Tony, I'm not playing around, did you even consider what could go wrong if we did this?" Banner, formerly known as the Hulk, stared at Tony pleadingly as he palmed his hand into his head.

"And did you not even consider what this could mean for us… for humanity?" Tony peered into Banner's eyes as if expecting validation.

"You cannot change where I stand on this. I am not going to go into human modifications just to create some kind of weaponized human, did you not learn anything from what happened with Ultron!?" Banner would not budge on his decision no matter how much Tony urged. He had been a victim of Tony's ideas far too many times. Even though they had made it so far in their experiments, one can only say that luck has protected them thus far.

"Come on buddy. Everything turned out okay. This is not as big as the whole artificial meteor almost ending humanity thing. We aren't creating anything with a consciousness, just modifying something that already exists … a little." He shrugged his shoulders.

"You just don't understand do you? First you save New York, but then you have to cancel it out by creating a rebellious kill bot who tries to destroy the world just to get out of your shadow. Yes, we are scientists; but, even more importantly, we have things we must protect. Creating another weapon is like giving a gun to a passerby in front of the group without knowing whether they are friend or foe. We may have control over who creates the first weapon of its kind, but not who buys it, sells, it and uses it." Banner trusts Tony, but sometimes he just cannot understand him. He stares, hoping at least something in this speech has gotten to him.

"Well. First of all: WE created the kill bot; and second of all, you're right, I don't understand. If we don't do it, someone else will, and we won't be ready for it. How many times do I have to point out that this is not a fair fight? Maybe you are willing to run away from this like you do from women, but I'm not" Tony held his ground. He knew that he could easily beat Banner in a word battle because he was always soft on him. Feeling as if he had an advantage over the silence, he then peered into Banner's eyes once more. "Look man, if we do this maybe we can even find a way to get your body back."

"Look, I'm not doing this with you again. Call me a coward all you want. It's not that I don't fight, it's that I fight different battles than you do," he said as turned away from Tony and looked down at the table. He knew that the glint he always saw in Tony's eyes may once again turn all his efforts to deny into folly.

"Hulk, while you fighting battles on the inside, the battles happening on the outside, the world will not wait for you." He grabbed Banner's shoulder and passionately stared into his eyes. At that moment Banner knew, he fucked up. Why didn't he leave as soon as Tony started this crazy talk? He could have run away like he always does. "If you know that something can go wrong in this, and that I am not going to stop until I get results, why not be here to make sure I don't make another mistake like the last time?"

Banner sighed, "Didn't you say that Ultron was OUR creation?" Banner could no longer contain his curiosity. At times like this he wonders if he is doing this for the good of humanity, or the thrill. Only Tony makes him question himself this way. He suddenly thought, "Does Tony do this knowing full well of the fact that I have a very thin thread of humanity keeping me from starting such dangerous experiments myself? Does he enjoy clawing out these dark inclinations I fight to keep at bay every minute of every day?" At moments like this he only feels defeat. He cannot forgive the Tony that tugs at the parts he hates about himself the most, but most of all, he cannot forgive the self that allows Tony to control him.

As if reading Banner's mind, he began to explain the game plan. "After you finish revising and refining all the fine details of the theories I've come up with thus far, I will get to building the equipment we will need for this. Feel free to come up with new theories yourself, go ahead and use the lab down stairs to run some tests, while I come up with some lame excuse for us to take time off the avengers."

"Do heroes get paid leave? Tell them we've caught the plague." At this point Banner lost his will to fight and could only go with the flow

"Buddy, you're a biochemist, couldn't you come up with a more plausible disease? Whatever, I'll get some make-up artist to make me look so sick I'm almost unrecognizable," Tony shrugged his shoulders as he changed from his suit to his sweat shirt and strode out the room.

"As long as you open your mouth and spew your usual sarcasm, they'll know it's you," Banner muttered just before Tony shut the door. Perhaps he needed to get in at least one snide remark to feel he did not completely lose his word battle with Stark earlier.

As he sat and looked over the notes left behind by Tony, he slowly seemed to recollect the conversation he'd had with him earlier. "Now that I think about it, there was a bit of desperateness behind his usual air of confidence this time around." Physically and verbally everything seemed the same, but as one who has become so close to Tony, it is as if he has developed a sixth sense. "He seemed uneasy, like it was do or die. We have had this conversation several times before, but this time around, the atmosphere was slightly different." As he read further and further into the notes his worries only continued to grow. "This is amazing, how long did it take for him to configure all of this by hand?"

A week passed after Tony's proposition and they diligently continued their work getting only two to four hours of sleep a day. Banner decided to closely analyze Tony's actions to confirm his suspicions of Tony's behavior. As he thought, he is definitely hiding something important from him.

"Hey, Greeny, pass me those notes." Banner scurried to pass the papers to get back to his experimentation log as soon as possible.

"So, I know that we are a week into this and it's kind of late to be asking this but… Why the sudden interest? I mean, why not stick to your robots instead of getting all tangled up in the modification of the human body?"

"Hmm, it was just. You know? Like, WHAM! And a voice in my head said why not use the tool we are born with, the human body. Well don't get me wrong, I still prefer my machines. When human thoughts and emotions get involved things always g o whacky." Tony started to ramble nonsense as if it were a matter of fact.

"I'm sure you're not the first to think of this. We have people on our team that have body modifications but it never seemed to compel you to do anything." He knew he would not get a straight answer from him, but it was worth a try. "You know what, never mind. Come check this out." As their experiments unfolded the direction seemed more like they were researching a biomechanical all-purpose cure, accompanied by enhancement. At first he thought that Tony just wanted some type of precaution in case something went wrong with the test subject (namely himself since they could not bring themselves to harm any living thing as heroes). But Tony only lightly goes over any talk of eventually developing it into an actual modification due to the condensed energy packed into the molecules that could create super human strength on all modified locations of the body whether it be the heart, bones, or skin after the procedure. It is becoming more of an immortality drug. Banner, occasionally chuckled to himself with delight from curiosity, and spite because he felt it to be impossible to give a person immortality.

As the weeks quickly became months, Banner slowly began to realize that the impossible was possible. If this drug and machine were used on a person, they may have the potential to become immortal. The subject would be able to absorb energy from its surroundings and replenish their cells directly by ingesting blood or raw meat almost as if they were absorbing cells to directly replenish its own. The molecules making up its tissues would be too strong and tightly bound to be harmed by something as small as decomposition; if they lose too much energy, they will simply go into suspended animation until enough energy is gathered. Their body would be like that of a vampire, immortal, super human strength, and could even take the excess energy from living creatures without touching them to sustain itself. This is worse than a weapon, "Humans are the true monsters," Banner muttered between gasps. "And I am giving this monster a stronger vessel."

"Hulk, buddy, you want some lunch?"

Shocked out of his realization, he blankly stared at the Bucca bag and uttered, "… Sure." He had no idea how he was going to convince Tony out of this. They had come too far, there was no way he was going to let it go. But there was still time, oddly enough, the Tony that is so obsessed with technology made sure all experimental logs, procedures, and notes were hand written; they could still be disposed of without being detected. Even he, within in all his fear he felt a certain amount of excitement. Once again he felt defeated by Tony's words that always seem to have a deep fragile truth under his usual playful tone. Tony was right, he is a mad scientist.

Tony only seemed to stare at Banner barely laying a hand on his food as if he were analyzing him.

"What's wrong? You're the one who bought the food, why aren't you touching it?" He almost couldn't help but to laugh at the irony of his question, 'what's wrong.' There was so much wrong he didn't even know where to begin. He started to feel dizzy as if his realizations were just too much.

"…" Tony only looked away, completely ignoring the question.

"Hey, why aren't you saying anything?" Banner said with slight unease. Again his vision began to blur, slightly more than before. As he probed Stark for an answer, his vision only began to blur more and more as his legs began to buckle and his sense of touch went numb, only serving to heighten his unease.

"… Tony!..."

Tony finally stood up, but only to walk away.

Upon seeing Tony leave, Banner could no longer find it in himself to hold on and fell to the floor losing consciousness.

Upon twenty minutes after passing out Banner found himself in the machine him and his accomplice had just built. For a few moments, he could only stare in disbelief. Then, before he could yell out to talk reason into Tony he was interrupted by Tony's unusually cold and calm voice.

"I knew I couldn't knock you out for long, but this is just outrageous."

"Tony, why?" His voice almost cracked from the shock.

"Why, you ask? Because I have no choice of course. I have already injected you with the drug, if I don't turn on the machine and infuse it into you, the drug will simply eat away at your energy instead of feeding it to you through your environment. There's no turning back now. Don't worry, I gave you suppressants so you won't turn green right now."

"That's not an answer!" Banner barely managed to raise his voice.

Completely ignoring his outburst, "Come on, you should be happy, if this works like we created it to, your body will only be controlled by emotion as much as the next person, you'll just be faster, stronger, and a little immortal. Don't worry, I won't use this on anyone else, I'll destroy the work after I'm done so chill and listen to some elevator music. It's quite soothing actually."

Once again Banner was overcome with dizziness as he stared at the man he thought to be his best friend look down on him from above.


	2. Chapter 2: Cause and Effect

Chapter 2

-Several days later

This time, Banner woke up in what seemed to be Tony's bedroom. It felt as if it were only a few moments ago that he was confined to the machine, but he knew better. His newly altered body probably went into a deep sleep as his body began adjust and absorb the energy around him.

"How ya doing buddy?" Tony was as casual as ever. "I ran some tests while you were out. You didn't wake up for over two weeks, it seems like your body just needed time to stabilize. Well at – WHAM!" Tony was suddenly found himself pinned against the window next to his light stand still managing to muster up a joke, "Well good thing this window is bullet proof. Now we know it's Tony Stark proof. *cough."

"Give me a good reason why I shouldn't tear you into a million pieces."

*cough, cough, "Well, why not? You're clearly capable. If there's an opportunity to get what you want, then take it."

"TONY, I don't have time for your sick jokes!"

"Um, Correction, you do have time. You're immortal now, remember?"

Banner then threw him to the floor, "Do you not understand how much it is taking for me to not to use all of my physical strength on you right now? Don't test me."

Tony only chuckled under his breath as if it did not matter either way as his back landed against the wall.

"We have been through too much, we have seen too much for you to not only turn your back on me, but to actually betray me. There were many instances where I could not make you out Tony, but I always trusted that your heart was always that of a human that can sympathize with pain. I thought that was why you always protected yourself with your sarcasm. But now, I can only see you as a sociopath that does not know how to play with his toys without breaking them." Overcome with a sense of loss of a dear friend, his anger subsided only leaving him with sadness. "I didn't ask for this. You know I would never ask for this power. It is almost as if I'm always Hulk now."

Tony finally stood up and motioned as if he were leaving the room.

"You never say what's important." Banner said with disdain.

"Like you're any different. I'll give you some time to think this over. As it stands I am the only one who knows of your condition, and I'm sure you would like to keep it that way. Your cells should have evolved enough for you to take on his form at will." He turned away, left the room, and closed the door.

"Why did I let him pull me into this? How is it that he is able to simultaneously make both my wildest dreams and my worst nightmares come true? I can't even hate him for it, it's my own fault. I'm always free to make my own decisions." Banner knows exactly why he can't leave Tony. It's not just for the sake of experimentation, it's not because Tony is his only friend, and it's not out of pure admiration for his confidence. "I have to find him." Just as Banner motioned to open the door he sensed Tony…

*Click* "Oh, what's up? I was just about to ask you if you wanted to eat. I mean, it probably won't do much for you considering you have not eaten or used the bathroom for a whole two weeks and you still look completely fine. OH! And this time, no surprises!" He cheerfully said with a mischievous smile.

"Tony, you don't look well."

"What are you talking about?" Tony averted his eyes as he laid out some snacks on the table.

"I know that you stayed by my side this whole time checking on my condition, trying to make things comfortable as I slept."

"Well of course I did, you're my precious green guinea pig! Oh yeah, guess you won't be turning green so often anymore, I'll miss that big guy."

"Tony!" His voice deepened, "You're not like the rest of us, you are still human. You are so frail; do you not even understand how easy it would be to snap your neck?" He slammed Tony against the door by his neck. "I only have so much patience."

Tony laughed again as he gasped, "Do it, what have I done to deserve your pity." He put on a brave face despite the hand slowly gripping tighter at his neck and his obvious exhaustion from lack of sleep.

"I can't help you if you never explain anything. Why did you do this? You didn't even tie me down in fear of what I could do to you." He lightly loosened his grip, but Tony was still pinned against the wall.

"Heh, your actions don't match your words. How can you still manage to be a complete dork despite gaining so much power?" Tony did not bother to struggle since he knew he stood no chance.

Cough cough* Banner could no longer manage; he threw him to the floor. "Time and time again you claw out my demons." He was done reasoning with Tony. This was getting him nowhere. He then let go of Tony's neck allowing him to slide to the floor catching his breath, he motioned himself over Tony's body, which rested on the door. "How are you able to keep your cool in this condition?" He thought to himself while then gripping Tony's arms together with one hand.

"Hey, if you're going to kill me, then do it quickly. The suspense is killing me." Tony could now speak more clearly with Banner hand removed from his neck.

"…" Banner replied with silence. He was stunned, he never thought there would come a day when he is this deathly calm while Tony was this uneasy and defenseless. "See how it feels to not understand what one is thinking," he thought to himself. He suddenly gripped both of Tony's hands and tied them with the tie laying on Tony's night stand.

"Hulk, buddy. I only like to be tied up by women." An uneasy smirk crossed his face in a futile attempt to hide the dread.

"…" If he is not going to listen to reason, I am going to quit desperately holding on to reason. He then pulled Tony's waist into his lap and groped his chest with both hands. "You never listen to what I say, so why should I listen to you. Be patient, I'll kill you when I am done."

"I know I kind of altered your chemical configuration without permission, but come on now. We all make mistakes." His pulse began to race. It's not that he didn't think he deserved whatever he's got coming to him, it's just, he never saw this one coming.

As if not acknowledging anything that was said, he lifted Tony's shirt and began to lick and nip at his nipples.

*Gasp. "Ngh! Stop!" Tony's body tensed.

"Hm, you are a man so I guess it's not all that stimulating." He then unzipped Tony's pants and jammed his hand into his underwear without warning as he continued to caress Tony's nipples with his tongue. His hand slowly began to jerk Tony.

"Banner! This is not you! You're… supposed to be the good one." Tony's face became more complexed as he tried to wiggle away despite being sandwiched between Banner and the door. Even as he tried to reason with Banner, he could only feel Banner's awkwardly dry grip grasp tighter.

"And just what is it that you know about me? Aren't I just your test rat that you use whenever you feel like it? By good you mean obedient." He gripped Tony's dick even harder.

*Gasp* "Banner, stop! It's disgusting!" And it hurt like hell, there were too many things wrong with this development.

"You don't really seem to be grasping the situation here." Banner then lifted his head and gestured near Tony's shoulder. "Right now your life is at my mercy, that makes you mine to do whatever I want with." He then bit into Tony's shoulder causing his body to jerk as he let out a silent scream. Tony desperately wiggled and squirmed as Banners teeth sunk further into his pulsing flesh. "This… why do I feel so much pleasure from this. I am seeing a new side of Tony in such a backwards kind of way. Rather than feeling anger, now, I only feel a strong thirst for more. I no longer feel the restraint from having to hold myself back from turning, nor the fear and sadness of hurting someone dear while barely being able to remember. I feel free. I almost can't even remember why I am hurting Tony like this… I just want him so much, and now I have the power to take him." As these thoughts rushed through his mind, he continued to relentlessly grope Tony and recklessly licked up the blood pooling from Tony's throbbing neck.

"Haa haa, mph." Tony attempted to muffle his moans by biting his lips but it only tempted Banner to pry his lips open with his tongue. "Mmmng!" He tried to stay quiet because of his sense of pride, but every breath felt like a whimper which only served to further fuel Banners passion.

Banner finally removed Tony's pants and underwear completely and started to roughly caress the rest of his body. He wanted to take it slow, truly, he wanted to slowly savor the taste of a defenseless Tony, but his unrelenting desire to mess him up got the better of him. His hands and tongue traced along his thighs, to his stomach, past his chest, and up to his neck. "Let me hear you." Banner whispered into Tony's ear.

Tony replied with a weak smile, "Just hurry and get it over with." It was obvious that he was scared. It seemed as if tears could trickle down his flushed face any second.

Banner let out a soft chuckle, then fiercely shoved his fingers down Tony's throat. "I am going to do you," Banner whispered into his ear as if to make Tony's situation more real by putting it into words.

Without warning, Tony chocked and grasped for breath, his pleading to stop only fell short of a moan. "RRGH!" Tony stared into Banner's eyes pleadingly.

As if to respond, Banner removed his fingers.

"Are you a Fucking idiot!? Cough* Cough*" Tony stumbled as he tried to both grasp for breath and hoist himself off the door. "You can't be serious, and even if you were, this isn't some porno where you can just moisten your fingers a bit and shove it up my - Mmph!" He was then interrupted by Banner gripping his dick yet again.

"Didn't I say you were mine?" he then motioned his fingers to Tony's bear entrance and forcibly probed his outer walls with his moistened fingers, he then shoved in two fingers without warning. The moment he slipped them in, Tony's back arched forwards and the tears and tension he had been restricting all the while were finally released with a loud moan. "Aaaaargh, ngh!" Banner's fingers slowly made their way in despite the resistance of Tony's body.

"Hmm, it's tight." Banner's eyes were fixed on Tony, examining his expression – painted with discomfort, pain, and a hint of sadness – as well as Tony's form, which he could not tell was shivering from pain or pleasure. But the sight of Tony's muscles contracting up and down only proved to excite him.

Tony finally began to thrash around as violently as he could despite knowing the futility. "Why won't you just hurry up and take your revenge by killing me? Don't tell me you just can't bear to kill your master yet!? Can't give up being my cute little green guinea pig?"

Banner was no longer affected by Tony's harsh words, or rather, he no longer cared. "Why do you want me to kill you so badly," Banner replied in a jokingly manner. "All this talk about death is killing the mood." He continued to prepare Tony from behind, slowly pulling in and out while alternating between 2 and three fingers, as he used the other hand to grope the front. When he was done, he finally spread Tony's legs, then ass cheeks, and exposed his raging boner which had been seen bulging in his pants only moments earlier. He had almost cum several times just from the thought of eventually penetrating Tony and having his way with his body.

"No, stop it Banner! This isn't who you are! Don't do this!" Tony could not stop the tears rushing down his face as he tried to move his ass away from Banner.

Without waiting a second longer, he penetrated Tony to his deepest depths. After meeting a little bit of resistance he slid his dick deeper and deeper into Tony's body. Once again Tony let out a silent whale as he struggled to breathe.

"Ngh, urgh! S..Sorry I came, it's been a while." Banner proclaimed as he winced at the tightness, at this point his voice had become nearly as rugged as Tony's, but rather than from pain, it was purely pleasure.

"Since… you're done… take it out." Tony was still struggling to breathe and his bottom was still propped up in Banner s lap, joined at the hip. Unfortunately, it had long since been too late for him to get away.

Suddenly turned on again by Tony gasping underneath him, he suddenly began to thrust in and out slowly. It was easier to thrust with his cum being made into a lubricant for his ass. He could never get enough of seeing such extreme expressions in Tony as he clawed at Banner's chest and bit his lip in a fruitless attempt to hold in his voice. Tony was beautiful.

"Please, enough." Tony could no longer bear to yell insults, only release small whispers accompanied by gasps when the pain became too much to bear.

"It's not over yet." Banner began to thrust harder and harder, not giving Tony's body a moment's rest as he began to violently pump Tony's cock again. With each thrust, Tony's insides seemed to become smoother.

Tony only wanted this pain to end as quickly as possible. He did not understand how he somehow managed to get hard from this nonsense like some masochistic pervert; it was his mind's way of escaping the pain.

Banner began to lick the mark he had left on Tony's neck, then sucked it with a fierce force as if he were a vampire captivated by the mere scent of a mortal.

Tony's world began to tremor and swirl as his body was finally at its limit; it did not help that his body was already weary from countless sleepless nights of looking after Banner after the procedure. He could no longer think straight, the only thing that was clear was Banner's face, the face of the man he broke without a second thought. Before his consciousness faded he came together with Banner in his hand while softly speaking his name. "H-Hulk," he managed to whisper in his ear as his body fell limp due to his fading consciousness.

Banner licked the last tear coming out of Tony's eyes as he caught his head to stop it from hitting the door. "Why did you have to go and say my name like that," he chuckled under his breath as the pain and heart ache came surging back. His lust was spontaneously replaced with deep concern. He can never understand what Tony is thinking, but… If he really were a self-centered being who wanted to play around with immortality, why would he give him immortality while leave his body unprotected despite knowing full well that he could possibly go into a rage and end his life? Why would he destroy the research after using the complete product only on him, what happened to piecing our time? Why did he keep trying to discard his life? He knew that Tony was the type to mask his fear with rash decisions, but what was it that had him so afraid? It obviously was not his health; he is confident, but cautious. He pondered this all while he gently washed Tony in the bath and clothed him (making sure to thoroughly clean the cum from his ass). He then put him to bed and watched him through the night. "Why didn't you give me telepathy while you were at it?"


End file.
